Peoples Drug Stores bucked the trend toward sagging corporate profits by registering a gain in net income of 17 percent for the fourth quarter and 13 percent for the year.

Alexandria-based Peoples posted 1982 profits of $10.5 million ($2.09 a share), compared with $9.3 million ($1.91) in 1981.

Revenues increased to $688.4 million from $634.3 million during the year.

Fourth-quarter earnings were $2.9 million (57 cents) on revenues of $162.8 million, compared with earnings of $2.5 million (50 cents) on sales of $143.2 million in the same period last year.

"Peoples' strong performance, especially in the fourth quarter, is the product of aggressive merchandising programs to increase market share, combined with strong emphasis on internal controls that directly affect our bottom line," said Chairman Adrian C. Israel and President Sheldon W. Fantle.

Peoples' earnings reflect a five-for-four stock split on Oct. 6.

Maryland Cup Corp. of Owings Mills, which manufactures paper and plastic food service products, reported earnings of $14.1 million ($2.05) for its fourth quarter, a gain of 5.4 percent. Revenues declined to $185.8 million from $194 million.

Earnings for fiscal 1982 rose by 4.2 percent to $31.7 million ($4.66) on sales of $655.9 million, compared with $30.4 million ($4.52) and sales of $647 million for last year.

Yearly results reflect a gain of $1.02 million (15 cents) from the exchange of $3.4 million of its sinking fund debentures for 73,739 shares of its common stock.

Computer Entry Systems Corp. reported an 82 percent plunge in profits for the third quarter. Earnings were $102,000 (3 cents) on sales of $3.3 million, compared with net income of $554,000 (15 cents) on revenues of $3.4 million in the year-ago quarter. Net income for the nine months of 1982 was off 14 percent, to $976,000 (25 cents) from $1.1 million (31 cents). Revenues increased to $11.3 million from $9.1 million last year.

The results, which the firm said were expected, reflect "significant legal and accounting costs incurred with the acquisition of Amer-O-Matic, increased research and development and introduction of new products, as well as general economic conditions." During the third quarter of this year the Silver Spring company spent $370,000 for software and hardware development. It also reported receiving new orders in the last 30 days amounting to $1.2 million for its optical character recognition business.

Bresler & Reiner, Inc. experienced a 55 percent drop in earnings during the third quarter, to $691,000 (63 cents) on revenues of $4.3 million, compared with net income of $1.5 million ($1.39) on sales of $4.5 million in 1981.

For the past nine months, the company earned $1.3 million ($1.14), compared with $4.4 million ($4) during the same period last year, while revenues declined to $11 million from $15.6 million. Chairman Charles S. Bresler explained that the 1982 nine-month results included gains on the sale of realty interest of $540,000 while the 1981 results included $4.5 million of such gains.